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767 Accident In '91-thrust Reverse Caused?

Sun Oct 19, 2003 12:59 pm

I just read an excerpt about that incident. Can anyone please explain what occurred? I had never heard of this occurring.

A 767 crashed in 1991 b/c a thrust reverser engaged in flight??

thanks, mirrodie
Forum moderator 2001-2010; He's a pedantic, pontificating, pretentious bastard, a belligerent old fart, a worthless st
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RE: 767 Accident In '91-thrust Reverse Caused?

Sun Oct 19, 2003 1:14 pm

May 26 1991 Lauda Air flight NG004 departed Bangkok for Vienna. Whilst on climb through FL 247 the left engine thrust reverser deployed which then overstressed the airframe and caused the aircraft to break up. I believe it was an electrical problem which caused the reverser to inadvertently deploy.

RE: 767 Accident In '91-thrust Reverse Caused?

Sun Oct 19, 2003 1:17 pm

That was the incident that resulted in the 180 KIAS limitation on the arming of the thrust reversers on many transport category jet aircraft.
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RE: 767 Accident In '91-thrust Reverse Caused?

Sun Oct 19, 2003 3:51 pm

Boeing 767-3Z9(ER) OE-LAV "Wolfgang Mozart" had ongoing problems with her left engine thrust reverser system.

Climbing out of Bangkok the 'REV ISLN' light illuminated several times as the reverser started to deploy and was restowed by the auto-restow function. Eventually the reverser sleeve opened, and due to the mounting of the engine forward of the wing airflow was disrupted and great stress was applied to the airframe.

The aircraft completely broke up 29 seconds after the thrust reverser deployed. Investigators claim that their was only six seconds where the aircraft could have been saved, impossible for the unsuspecting crew.

Very nasty.
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RE: 767 Accident In '91-thrust Reverse Caused?

Tue Oct 21, 2003 3:48 pm

Firings, if well done, are good for employee morale.
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RE: 767 Accident In '91-thrust Reverse Caused?

Wed Oct 22, 2003 3:43 am

This incident also prompted the various AD's to install a third line of defence for ALL commercial aircraft T/R's. Previously there was only one level of failsafe designed into the T/R system, now there are two levels (i.e there has to be two separate system/component failures before the T/R is at risk of deploying if another system/component fails) or, in other words, an additional level of redundancy.

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RE: 767 Accident In '91-thrust Reverse Caused?

Wed Oct 22, 2003 3:46 am

BM-1 oh you can tell 'em about it just it's it's it's
just ah no- ah it's probably ah wa- ah moisture or
something cause it's not it's not just on it's coming
on and off


BM-1 but oh you know it's a- it doesn't really it's just
an advisory thing I don't ah

.....and later still.....

BM-1 could be some moisture in there or somethin'

These are the words of the captain, personally I've always felt he sounded very complacent, like he was trying to make the co-pilot feel at ease.

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RE: 767 Accident In '91-thrust Reverse Caused?

Wed Oct 22, 2003 11:26 pm


What is "arming the thrust reverser". I've heard of arming the speed brakes but reversers are inhibited in the air. The only exception I know about is the DC8 which allows deployment under certain operational circumstances.

This is an excerpt from the B767 AMM and is fairly typical of transport cat. airliners:
"An electrical circuit to operate the thrust reverser pressure regulating and shutoff valve (PRSOV) to provide pneumatic pressure to the reverser actuation system. The electrical circuit also prevents reverser operation unless these required operating conditions are met: (a) The air/ground relays are in the ground position. (b) The fire switch is in the normal position. (c) The thrust reverser position switches are in the reverser stowed position."

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